Lévy joined Publicis in 1971 as its IT director. One of his most important feats was putting in place a data security policy, which involved backing up all of the company's data on magnetic tape. A fire in the company's office (on the Champs-Elysées) proved the success of his backup and restoration strategy, as the company was back on its feet one week later. He then became the anointed successor of the company's then owner and Chief Executive, Marcel Bleustein-Blanchet, who made him Chairman of the Management Board, and Chief Executive Officer in November 1987.

Since the death of Bleustein-Blanchet, Lévy has not only become the strong man of the company with the full backing of Elizabeth Badinter—the heir of Bleustein-Blanchet—but he has also succeeded in transforming the group into one of the powerhouses of the advertising world. Today, the Publicis Group is the world's 3rd largest advertising and media conglomerate, and Lévy is one of the most influential men in France and in advertising worldwide.

On 28 July 2013, Lévy announced the merger of Publicis and Omnicom to create the world's biggest advertising firm. The merger ultimately failed, but Publicis extended Lévy's term as CEO.[2]